As an example of a display device, an organic EL (Electroluminescence) display device is represented. An organic EL display device possesses an organic light-emitting element (hereinafter, referred to as a light-emitting element) in each of a plurality of pixels formed over a substrate. A light-emitting element has a layer (hereinafter, referred to as an EL layer) containing an organic compound between a pair of electrodes (cathode and anode) and is driven by supplying current to the EL layer from the pair of electrodes.
Efficiency and emission color of a light-emitting element are controlled by a structure of the EL layer and an emission material included in the EL layer. For example, appropriate selection of an emission material enables light emission with a variety of colors. Additionally, it is also possible to adjust an emission wavelength and increase emission intensity in a front direction by utilizing light-interference effects in or outside the light-emitting element. Japanese Patent Application Publications No. 2017-112011, 2017-62902, and 2017-107181 disclose that a resonance structure is formed in a light-emitting element to allow light emission obtained from an emission layer to resonate, thereby adjusting emission intensity and emission color.